超声速二维进气道非设计工况激波串运动特性

Motion Characteristics of the Shock Train in a 2D Supersonic Inlet at Off-design Conditions

本文针对超声速进气道在非设计工况下由背压爬升引起的激波串运动问题,采用非定常数值模拟,研究了设计马赫数为3.3的二维进气道在来流马赫数Ma_(∞)=2、3和4时的激波串运动特性.结果表明,不同Ma_(∞)下,激波串前缘激波的运动过程均可分为三个阶段:初始背压主导的快速前移段(阶段Ⅰ)、顺压梯度区主导的缓慢前移段(阶段Ⅱ)、背景波系和肩部分离区主导的剧烈干扰段(阶段Ⅲ).在阶段Ⅰ和阶段Ⅱ,激波串前缘激波的运动特性类似,均先从进气道出口快速前移,在经历短暂后退之后,再次以较低的速度前移.在阶段Ⅲ,当前缘激波进入背景波系产生的逆压梯度区时出现突跳,而每次突跳的距离因Ma_(∞)而异.当前缘激波到达进气道肩部时,流动状态变化显著:Ma_(∞)=2时,肩部无明显分离区,前缘激波最终稳定;Ma_(∞)=3时,肩部形成了开式分离区,前缘激波轻微振荡;Ma_(∞)=4时,肩部存在大尺度的闭式分离区,并且前缘激波小幅振荡,导致进气道的脉动压力系数明显增大.

The motion characteristics of the shock train caused by backpressure are investigated in a supersonic inlet at offdesign conditions.Unsteady numerical simulations are performed to reveal the effects of inflow Mach number Ma_(∞)=2,3 and 4 on the motion of the shock train in a 2D inlet with a design Mach number of 3.3.The results show that the motion process of shock train can be divided into three phases at different Ma_(∞):the fast moving forward segment dominated by initial back pressure(phaseⅠ),the slow moving forward segment dominated by favorable pressure gradient region(phaseⅡ),and the intense interference segment dominated by background waves and shoulder separation bubble(phaseⅢ).In phaseⅠandⅡ,the motion characteristics of the leading-edge shock in the shock train are similar,which moves forward quickly from the outlet at the beginning and then moves forward slowly after a temporary retreatment.In phaseⅢ,a sudden jump occurs when the leading-edge shock enters the adverse pressure gradient region generated by the background waves,and the jump distance varies with the Ma_(∞).The flow features in the inlet change significantly after the interactions between the leading-edge shock and the separation bubble on the shoulder.No obvious separation occurs on the shoulder and leading-edge shock is finally stable at Ma_(∞)=2;an open separation occurs on the shoulder and the leading-edge shock oscillates slightly at Ma_(∞)=3;and a large closed separation occurs on the shoulder and the leading-edge shock oscillates with a small-amplitude at Ma_(∞)=4,which leads to a significant increase in the fluctuating pressure coefficient.